No, you don't weigh the feather...that would be ridiculous, as you would be determining the weight of the feather there. I would assume he is suggesting that you apply a known force to a feather and measure the acceleration, thus determining the mass.

No no no no...neglecting air resistance would be super bad. I said a known force. If you have air resistance, unless you can somehow precisely determine it, you'd have an unknown force. I would suggest doing it in a vacuum, probably in microgravity. That way you could just set up some kind of force application system like a laser beam to make it work. Of course, measuring the exact acceleration would be difficult, but I would guess you could cheat by setting up your experiment far away from other gravitating and light emitting bodies, and then apply said laser push over a long period of time, measuring the velocity. Don't forget to take the gravitational effect of your laser/measurement system into account though. I think you could fairly reasonably determine it's mass that way, for certain definitions of reasonable.

Make an identical feather out of antimatter. Collide inside thick shell of lead surrounded by vacuum. After a long time (but not too long!) measure the change in temperature of the shell. Add E = mcc, stir.

nilkemorya wrote:Don't forget to take the gravitational effect of your laser/measurement system into account though.

Yeah, and if the feather rotates at all don't forget the geodetic and frame dragging forces either. Also be sure to renormalize its quarks.

I dunno, it seems like if you just put the feather on a triple beam balance and then put a weighing boat on top of it you would get a result for the mass that, although it would have orders of magnitude fewer significant digits than the answer produced by Nilk's most excellent and refined approach, would probably be good enough for science.

And I remember some reading about some scientist or another who once tried to weigh souls as they escaped dying people (don't remember all the details offhand). So find those numbers and use them. Or go collect your own data. "Now hold still. Remember, it's for science."

Citizen K wrote:And I remember some reading about some scientist or another who once tried to weigh souls as they escaped dying people (don't remember all the details offhand). So find those numbers and use them. Or go collect your own data. "Now hold still. Remember, it's for science."

Thanks to the astonishing advances of science, we now know that the mass of the human soul is 28 grams - a figure definitive enough to base a movie title on. Aren't we fortunate to live in an age where this need no longer be a matter of guesswork?

"The age of the universe is 100 billion, if the units are dog years." - Sean Carroll

nilkemorya wrote:I would suggest doing it in a vacuum, probably in microgravity. That way you could just set up some kind of force application system like a laser beam to make it work ... apply said laser push over a long period of time, measuring the velocity. Don't forget to take the gravitational effect of your laser/measurement system into account though.

Also, be sure to take into account the absorbance and emission spectra of the compounds the the feather, as well as the efficiency of that transfer. You will not only have to take the loss of efficiency in acceleration, but the opposing accelerative forces as energy is radiated away. These may cancel out, as the radiative energy should be equal in all directions, but this may vary with the geometry of the feather.

Also, as you will be applying a significant force over a period of time, be sure to take relativity into account. Of course you'd take the mass effect into account, but you'd be surprised how many people neglect time dilation and its effects on measured velocity (distance/time).

ATCG wrote:Thanks to the astonishing advances of science, we now know that the mass of the human soul is 28 grams

Correction, that's 21 grams. Anyways, this type of sciencing also alledgedly showed travel above 20mph to be deadly for lack of oxygen.

For what it's worth, 1 gram for a feather sounds far to much. As in, more than an order of magnitude. Consider that a falcon weighs something like 150--200gr and has some about as many (sizeable, force-bearing, not downy) feathers. You see, most mass is in the body so the feathers must be less.1gr would be the weight of a 1cm cube of water --- pigeon's feathers have clearly less volume and are also known to float (that may be due to the hollow shafts though).

ArmonSore wrote:But once you accelerate it to a new velocity the mass changes

That depends on your reference frame.

Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

This is a placeholder until I think of something more creative to put here.

Well, if you only want the "practical" mass of a feather then you don't have to worry at all about the weird things that happen when you start to ask for something "exactly".

For example, I could ask you "what do you mean by feather"? And you show me a bird's feather. But on a microscopic level how do we know which molecules are feather and which molecules are air? What about the dirt on the feather which is constantly accruing and leaving?

nilkemorya wrote:No, you don't weigh the feather...that would be ridiculous, as you would be determining the weight of the feather there. I would assume he is suggesting that you apply a known force to a feather and measure the acceleration, thus determining the mass.

Or perhaps put the feather in a gravitational field so that acceleration is known, and measure the force applied to an instrument that can measure it

ArmonSore wrote:But once you accelerate it to a new velocity the mass changes

That depends on your reference frame.

Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

Oh, maybe I misunderstood what was said. I thought you were talking about taking an object, accelerating it to a new velocity, and then you stop accelerating it, at the new velocity.

nilkemorya wrote:No, you don't weigh the feather...that would be ridiculous, as you would be determining the weight of the feather there. I would assume he is suggesting that you apply a known force to a feather and measure the acceleration, thus determining the mass.

Or perhaps put the feather in a gravitational field so that acceleration is known, and measure the force applied to an instrument that can measure it

Except that you'd need to know the position of the feather and the earth exactly. So we're right back at the heisenberg uncertainty principle. And how would you measure the force? By looking at the deflection of a spring? That would require measuring another distance exactly.

evilbeanfiend wrote:obviously you use a standardized feather

The definition of a "standardized" feather would be even more dubious than the definition of a "feather".

ArmonSore wrote:The definition of a "standardized" feather would be even more dubious than the definition of a "feather".

Nah. Just define a standard feather to have a mass equal to, say, 1000000000000000000000 silicon-28 atoms. Then, when the new standard kg is produced, and they know how many atoms are in it, we'll know exactly what mass a standard feather has.

Shro wrote:I am the one who will teach the robots how to love.

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